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Changing Earth’s Surface EROSION Get ready for a demo!! What do you think of that? How cool would it be to go sledding down the sand mountain? What is erosion? • The process by which wind, water, ice, or gravity transports soil and sediment from one location to another. Short Movie Clip! Erosion by Water and Ice • Pounding waves break rocks into pieces and wash them away • Currents move sand down shore • Running water creates ditches • Glaciers carve through valleys as they move downhill Erosion by wind • Deflation – fine sediment gets blown to other locations • Abrasion – Particles blowing in the wind rubs against rock and wears it down • Particles blowing in the wind are deposited in other locations forming dunes and other landforms. WOW! This was the result of wind erosion! Angle of Repose • Mass movement is the movement of any material down slope. • Angle of repose is the steepest angle where material will NOT roll down slope. Types of Mass Movement 1. Rock Falls 2. Landslides 3. Mudflows 4. Lahars 5. Creep Rock Falls • Loose rocks fall down a steep slope. • Roads cut into a mountainside create steep slopes. Loose rocks above fall onto the road below. Landslides • Sudden and rapid movement of a large amount of material down slope. • Slump = most common type of landslide Landslide – Block of material moves down slope – Caused by heavy rain, deforestation, construction, and earthquakes SLUMP SLUMP Mudflows • Rapid movement of a large mass of mud • Caused by large amounts of water mixing with soil and rock • Increase chances with deforestation and removing ground cover. • • • Lahars Mudflows caused by volcanoes Travel fast! (80km/hr) Can be as thick as cement 1. Ice melts from volcanic eruption. 2. Water mixes with soil, rock, and ash. 3. Hot mudflow rushes downhill. Short Lahar Clip Creep • SLOW movement of material downhill • Caused by water, plant roots, burrowing animals and gravity. • You’ll see: bent trees, leaning poles, and cracked roads. What is…DEPOSITION??